Device for regulating blood flow

ABSTRACT

An implantable device for regulating blood flow through a blood vessel includes an elongated support. The support includes axially spaced apart first and second substantially annular support portions, and an x-shaped linking member linking the axially spaced apart portions to one another. The device also includes a valve membrane extending between the axially spaced apart support portions and having an upper portion, a lower portion and an intermediate portion. The valve membrane includes a first region and a second lower region. The first region is folded over the linking member for attachment and the second region is adjacent the first region and unattached to the linking member. The second region is movable between a first position to enable blood flow and a second position to inhibit blood flow.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/319,176 filed Jan. 2, 2009, and this application claimsbenefit of priority to U.S. Provisional Patent Application Ser. No.61/156,227 filed Feb. 27, 2009. U.S. patent application Ser. No.12/319,176 is a continuation-in-part of U.S. patent application Ser. No.11/801,489 filed May 10, 2007. Application Ser. No. 12/319,176 is acontinuation-in-part of U.S. patent application Ser. No. 11/801,691filed May 10, 2007. Application Ser. No. 12/319,176 claims benefit ofpriority to U.S. Provisional Patent Application Ser. No. 61/010,012filed Jan. 4, 2008. U.S. patent application Ser. Nos. 11/801,489 and11/801,691 each claim benefit of priority to U.S. ProvisionalApplication Ser. No. 60/808,406 filed May 25, 2006. U.S. patentapplication Ser. Nos. 11/801,489 and 11/801,691 each claim benefit ofpriority to U.S. Provisional Application Ser. No. 60/809,483 filed May31, 2006. Each of the applications listed above is incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention is directed to a device for regulating blood flowin the venous system, and more particularly, to an implantable valvedevice for regulating the flow of blood through a blood vessel.

2. Description of Related Art

The blood system, and in particular the venous blood system of the legsand arms is provided with valves that are uniquely located in a mannerso as to ensure that blood will not flow back upstream in the directionfrom which it has been pumped from the heart. In the arms and legs,there is a deep venous system and a surface (superficial) venous system.Due to various causes, thrombosis can occur in the deep venous system.Blood thinning can alleviate this problem. However, valves do noteffectively close and often leak when the blood in thinned. This cancause increased venous blood pressure in the direction of the ankles,which can lead to a variety of problems including pain, swelling,varicose veins and ulcers. Complaints of this type are wide spread amongthose who spend prolonged periods of time in a standing position, forinstance, surgeons.

The surface venous system of the leg is relatively weaker than the deepvenous system, and it has the tendency to spontaneously widen due to theincreased pressure of blood from above. This widening prevents thevalves from functioning effectively and can lead to varicose veins,which are both unattractive and painful. Major surgery is often requiredto treat these blood vessel problems. For example, varicose veins aretreated by either closing off the vein, which leads to a reduced bloodflow capacity and increased pressure on surrounding blood vessels toensure blood drainage, or by completely removing the varicose veins,which leads to the same problem. The deep veins require invasive surgeryand because of the swelling, risk of infection and trauma is seldomattempted. In either case, the treatment of the surface veins does nottreat the failed valves in the deep system, thereby causing thecontinued pressure and back flow into the legs. The subject invention isdirected to a device for obviating problems of this type.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful implantable devicefor regulating blood flow through a blood vessel. The device includes anelongated support dimensioned and configured to be implanted in a bloodvessel. The support includes axially spaced apart first and secondsubstantially annular support portions, and an x-shaped linking memberlinking the axially spaced apart portions to one another. The devicealso includes a valve membrane extending between the axially spacedapart support portions and having an upper portion, a lower portion andan intermediate portion. The valve membrane includes a first region anda second lower region. The first region is folded over the linkingmember for attachment and the second region is adjacent the first regionand unattached to the linking member. The second region is movablebetween a first position to enable blood flow and a second position toinhibit blood flow.

In certain embodiments, the device further includes a third regionfolded over for attachment to the linking member, with the second regionpositioned between the first and third regions. The linking member caninclude two curved members intersecting one another to form an x-shape.The support can be formed at least in part from a shape memory alloymaterial, or any other suitable material. The valve membrane can beformed at least in part from ePTFE, or any other suitable material. Itis also contemplated that the valve membrane can be coated at least inpart with an anti-clotting agent.

In accordance with certain embodiments, the device further includes asecond x-shaped linking member. The valve membrane can include a fourthregion folded over the second linking member for attachment. The upperportion of the valve membrane can be attached to a bottom region of thefirst support portion and the lower portion of the membrane can beattached to a top region of the second support portion. A section of thelower portion of the membrane can be wrapped around a section of the topregion of the second support portion. It is contemplated that thesupport can be integrally formed from a laser cut tube.

In accordance with certain embodiments, a first x-shaped linking memberlinks the axially spaced apart portions to one another, and a secondx-shaped linking member opposed to the first linking member also linksthe axially spaced apart portions to one another. The valve membrane caninclude first, second and third portions wherein the first portion isattached at a first region of the support, the third portion is attachedat a second region of the support, and the second portion is positionedbetween the first and third portions and is unattached to the support.The second portion can thus be movable with respect to the supportbetween a first position to enable blood flow and a second positioncloser to the support to inhibit blood flow.

It is contemplated that in certain embodiments, the first and a thirdportions of the valve membrane can form a flap wrapped around a portionof the support, and the second portion can form a flap movable withrespect to the first and third portions to create an opening forantegrade blood flow. The second portion of the valve membrane can becloser to a top region than to a bottom region of the valve membrane.

In certain embodiments, the valve membrane further includes a fourthportion separate from the second portion and unattached to the support.The fourth portion is movable with respect to the support between afirst position to enable blood flow and a second position to inhibitblood flow. The second portion can form a first flap adjacent the firstlinking member and the fourth portion can form a second flap adjacentthe second linking member. The flaps can each create a space between therespective flap and the respective linking member during antegrade bloodflow to enable blood flow through the space and the respective flapclosing the space during retrograde blood flow.

The valve membrane can be attached to the linking member, wherein thevalve membrane has an upper portion attached to a first section of thesupport and a lower portion attached to a second section of the support.The valve membrane can have an enabling condition to enable blood flowwhen blood flows in one direction and an inhibiting condition to inhibitblood flow when blood flows in an opposite direction. The upper attachedportion of the membrane and the lower attached portion of the membranecan remain substantially fixed in position in both the enablingcondition and the inhibiting condition and the lower and upper attachedportions can remain adjacent opposing regions of the vessel wall in bothconditions.

In certain embodiments, the valve membrane includes an intermediateportion between the upper and lower attached portions, and furtherincludes a first flap in the intermediate portion. The first flap can beunattached to the support and can be movable for creating the flowinhibiting and flow enabling conditions while the upper and lowerattached portions remain substantially fixed in position.

It is contemplated that the valve membrane can have a first regionunattached to the support, wherein the first unattached region is formedby at least one cut in the membrane. The first unattached region cancreate a first opening adjacent the support during antegrade blood flow.The valve membrane can also have a second region unattached to thesupport, the second unattached region being formed by at least one cutin the membrane. The second unattached region can create a secondopening adjacent the support during antegrade blood flow. It iscontemplated that the first and second openings can create a crosssectional shape ranging from about 15% to about 30% of the diameter ofthe vessel.

These and other features of the systems and methods of the subjectinvention will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject inventionappertains will readily understand how to make and use the apparatus ofsubject invention without undue experimentation, preferred embodimentsthereof will be described in detail hereinbelow with reference tocertain figures, wherein:

FIG. 1 is a perspective view of the flow regulating device of thepresent invention, prior to full assembly;

FIG. 2 is a perspective view of the support of the flow-regulatingdevice of FIG. 1;

FIG. 3 is a side perspective view of the flow regulating deviceillustrating how the membrane is attached to the frame;

FIG. 4 is a front perspective view of the top (distal) portion of theflow regulating device of FIG. 1 showing the membrane in the closedposition;

FIG. 5A is a side perspective view showing the membrane in the openposition;

FIG. 5B is a side perspective view similar to FIG. 5A showing themembrane in the closed position;

FIG. 6A is a cross-sectional view of the identified area of FIG. 5Ashowing the membrane in the open position, resulting from antegradeblood flow;

FIG. 6B is a cross-sectional view of the identified area of FIG. 6Ashowing the membrane in the closed position, resulting from retrogradeblood flow;

FIG. 6C is a top view of the upper region of the membrane of FIG. 5Bshowing the membrane in the closed position;

FIG. 6D is a top view of the upper region of the membrane of FIG. 5Ashowing the membrane in the open position;

FIG. 6E is a top view of the upper region of an alternate embodiment ofthe membrane shown in the open position;

FIG. 7 is a view similar to FIG. 4 showing another alternate embodimentof the membrane with flaps forming larger openings for increasedantegrade blood flow;

FIG. 7A is a cross-sectional view similar to FIG. 6B except showing themembrane of FIG. 7 in the closed position;

FIG. 8 is a drawing of the anatomy of the patient showing two examplesof locations of placement of the flow regulating device;

FIG. 9 is a front elevation view of the frame of a flow-regulatingdevice constructed in accordance with another embodiment of the subjectinvention with the membrane or sail removed for clarity;

FIG. 10 is a side elevation view of the frame of FIG. 9, showing one ofthe symmetrical x-shaped linking members connecting the two axiallyspaced apart ring portions;

FIG. 11 is a perspective view of the frame of FIG. 9, showing both ofthe symmetrical x-shaped linking members;

FIG. 12 is a front elevation view of the flow-regulating device of FIG.9, showing the membrane or sail in place;

FIG. 13 is a side elevation view of the flow-regulating device of FIG.12, showing one of the symmetrical x-shaped linking members connectingthe two axially spaced apart ring portions with the membrane or sailattached to a portion of the cross members of the x-shaped linkingmember; and

FIG. 14 is a perspective view of the flow-regulating device of FIG. 12,showing both of the symmetrical x-shaped linking members with themembrane or sail in place, shown in the flow restricting position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference numerals identifysimilar or like components throughout the several views, there isillustrated a flow regulating device constructed in accordance with apreferred embodiment of the subject invention, and designated generallyby reference numeral 10. Regulating device 10 includes an elongatedsupport 12 that has upper and lower substantially annular ring portions14 and 24, each having a series of rounded V-shaped apices 15 a facingin an upward direction and a series 15 b facing in a downward direction.That is, the upper or distal (with respect to the direction of bloodflow) ring portion 14 has a first series of angled struts 13 a forming aV and a second series of angled struts 13 b forming an inverted V whichtogether form a group of closed substantially diamond shaped cells 19connected at region 17. Similarly, the lower or proximal (with respectto the direction of blood flow) ring portion 24 has a first series ofangled struts 29 a and a second series of angled struts 29 b, facing inopposite directions and forming closed substantially diamond shapedcells 28 connected at region 27. The cells 28 have upper apices 25 andlower apices 26. For clarity, not all of the identical parts in thedrawings are labelled. Note that in the preferred embodiment, the ringsand linking member (described below) are preferably integral so thatterms “joined”, “connected”, etc. are used for ease of description.

Support 12 has two curved linking or connecting members 21 a, 21 b, bestshown in FIG. 2 in which the membrane is removed for clarity. The top ofeach connecting member 21 a, 21 b extends from a common lower apex 15 bof one of the pairs of angled struts 13 b of upper ring 14 (see alsoFIGS. 3 and 4) The lower end of connecting members 21 a, 21 b extendfrom separate upper apices 25 a, 25 b, respectively, of cells 28 oflower ring 24. In the illustrated embodiment, the apices 25 a, 25 b, areabout 36 degrees apart as ten cells are formed. However, a differentnumber of cells can be provided with different spacing between apices.Also, it should be appreciated that the connecting members can extendfrom other apices of lower ring 24 or upper ring 14. The connectingmembers 21 a, 21 b have a curve or twist extending close to about 180degrees (and extending substantially across the vessel when implanted)so that an upper end is connected to one end (viewedradially/transversely) of the device 10 and the lower end is connectedto an opposite end (viewed radially/transversely) of the device 10. Thatis, with ten closed cells in the illustrated embodiment, apex 15 b isapproximately 162 degrees out of phase from apex 25 a and from apex 25b. Other spacing and alternate number of cells is also contemplated.

Although two connecting members are shown, one connecting member or moreconnecting members could be provided. Also, the connecting members couldbe spaced further or closer apart and have different curves than shown.

The rings 14, 24 are collapsed to a reduced diameter (profile) positionfor delivery. The rings 14, 24, when implanted, are substantiallyperpendicular to the direction of blood flow. Preferably, the rings 14,16 in their expanded (deployed) configuration are larger in diameterthan the internal diameter of the target vessel to apply a sufficientradial force against the vessel to ensure that the device remains in adesired position and orientation after implantation. For example, foruse in an 8 mm vessel, the rings could have an expanded outer diameterof about 10 mm and preferably could be collapsed sufficiently to bedelivered through a 12 Fr (4 mm) delivery catheter. Others ringdiameters are also contemplated.

The support 12 is preferably composed of shape memory material, such asNitinol or Elgiloy, with a shape memorized larger diameter configurationas shown in the drawings. In the illustrated embodiment, the support islaser cut from a tube so that the connecting members and rings areintegral. However, it is also contemplated that alternatively thesupport can be formed from wire(s). Also, it should be appreciated thatinstead of being integral, separate members could be provided, withseparate rings joined by separate linking (connecting) members.

Device 10 includes a valve member or membrane 50 that is operativelyassociated with support 12 for regulating the flow of blood through avessel by moving between open and closed positions. Membrane 50 ispreferably formed from a sheet of ultra thin membrane material such as aePTFE material or the like. It is envisioned that the membranesdisclosed herein could be bonded or otherwise coated with ananti-clotting or anti-coagulant/anti-thrombogenic agent such as Heparinand/or an anti-proliferative coating, to retard the body's desire toreject the implant. In a preferred embodiment, the membrane is coatedwith an anti-thrombogenic agent and the frame is coated with ananti-proliferative agent, such as Dexamethasone by way of example.

As shown, valve membrane 50 has an upper portion 52, an intermediateportion 62, and a lower portion 72. With reference to FIG. 3 whichillustrates how the membrane 50 is attached to support 12 inmanufacture, the top portion 52 has first and second flaps 54, 56 whichare folded down over respective connecting members 21 a, 21 b andattached to the membrane to secure the upper portion 52 of membrane 50about the support 12. FIG. 3 illustrates flap 56 already folded in thedirection of arrow F4 from its unfolded position shown in phantom. FIG.3 also illustrates flap 54 in its unfolded position before movement inthe direction of arrow F3 in manufacture to its folded position depictedin phantom. Flaps 57 and 59 at the uppermost region of membrane 50 arewrapped around struts 13 b in the direction of arrows F1, F2,respectively.

With continued reference to FIG. 3, the intermediate portion 62 ofmembrane 50 has flaps 64, 66 for connection to linking (connecting)members 21 a, 21 b, respectively. Flap 64 is shown in a mostly unfoldedposition to be folded in the direction of arrows F6 to its foldedposition shown in phantom where it is attached to the membrane 50. Flap66 is shown in its unfolded position to be folded in the direction ofarrows F5 to its folded position depicted in phantom.

Lower portion 72 of membrane 50 has flaps 74 and 76 which are eachfolded around a separate strut 29 a. Arrows F8, F7, respectively,illustrate the direction of the fold.

Cuts in the membrane 50 create an unattached flap 84 between upperattached flap 54 and intermediate attached flap 64 and an unattachedflap 86 between upper attached flap 56 and intermediate attached flap66. These unattached flaps 84, 86 are positioned adjacent the respectiveconnecting member 21 a, 21 b as shown, but create a respective opening90, 91 for blood flow between the membrane 50 and connecting members 21a, 21 b as described below. Note, alternatively, the flaps 84, 86 canextend over the connecting member, as long as it remains unattached andcreates a sufficient space from the linking member to create asufficiently sized opening to allow blood flow therethrough.

Note that FIG. 1 shows the membrane 50 with the flaps open, prior toconnection in manufacture, to illustrate how it is wrapped around thesupport 12 and connected to other portions of the membrane forsecurement/attachment of the membrane to the support 12. The flaps,after wrapping over/around the region of support 12, can be connected tothe membrane body by welding, adhesive, suturing or other methods. Also,an intermediary material can be used to facilitate welding, such aspolyurethane or polycarbonate/polyurethane impregnated or otherwisecombined with the ePTFE material. It is also contemplated that themembrane can be attached to the support 12 itself by methods such as byadhesive or use of suture material.

As can be appreciated, the body portion of the membrane 50 extendssubstantially if not entirely across the expanse of the vessel in theopen position. However, the openings 90 and 91 adjacent the unattachedflaps 84, 86 provide a sufficient gap for the necessary amount of bloodflow, it being appreciated by applicants that a normally functioningvalve is only open about 35%. In some embodiments, the openings in themembrane created by the space between flaps 84, 86 and the supportcreate a space gap in the range of about 5% to about 15% of the diameterof the vessel. In the alternate embodiment depicted in FIG. 7, largeropenings 90′ and 91′ are formed to allow more antegrade blood flow. Inthese large opening embodiments, a space (opening) can be createdpreferably representing about 15% to about 45%, and more preferably fromabout 15% to about 30% of the diameter of the vessel. (In all otherrespects the regulating device of FIG. 7 is identical to that of FIG. 4and the corresponding parts are labelled by numerals with a primedesignation and therefore are not discussed herein). These percentagesare defined in terms of the diameter of the blood vessel. For example,if a rectangular opening is formed of dimension of 2 mm×4 mm, and isplaced in a 10 mm vessel, the cross section occupied by the two openings(about 16 mm) would be about 20% of the overall diameter of the vessel(about 78 mm). It should be appreciated that the foregoing ranges andpercentages are provided by way of example and other size openingscreating a different percentage opening are also contemplated. Also,other shape openings can be provided other than rectangular, includingsquare, semicircular, etc. FIG. 6E shows by way of example substantiallysemicircular openings 90″, 91″ formed by flaps 84″, 86″, respectively.

Movement of the membrane 50 between an open (blood flow enabling)position/condition to allow antegrade blood flow and a closed (bloodflow inhibiting position/condition) to essentially block flow are shownin respective FIGS. 5A and 5B, and shown in more detail in FIGS. 6A-6D.In the closed position, however, a minimal amount of blood flow isallowed as will be discussed below.

More specifically, and with reference to FIG. 5A, blood flowing throughthe blood vessel V in the downstream direction (antegrade flow)indicated by arrow “D” will act against the valve membrane 50 in such amanner as to push the body portion upwardly as viewed in the drawing,creating a concave belly on the underside. The blood will travel alongthe concave surface and up the membrane and the blood pressure willforce the flaps 84 and 86 upwardly, separating (spreading) them from therespective connecting members 21 a, 21 b as also shown in FIGS. 6A and6D to form an opening or gap.

After the pulsed blood travels in the direction of arrow D1 (FIG. 5A),through the openings (spaces) 90, 91, the blood backs up in thedirection of arrow C of FIG. 5B. This retrograde blood flow will actagainst the angled body of the membrane 50, forcing it downwardly asviewed in FIG. 5B to form a convexity on its underside. This downwardpressure will force flaps 84, 86 downwardly adjacent to the connectingmembers 21 a, 21 b, respectively, and against the connecting member asshown for example in FIGS. 6B and 6C, thus essentially closing theopenings 90, 91 to prevent blood flow therethrough. However, a smallamount of blood will force its way between the membrane 50 and thevessel wall as depicted by arrow C1 in FIG. 5B, thereby reducing stasisor stagnation that could lead to clotting. In embodiments wherein alarger flap is utilized to create a larger opening, such as in theembodiment of FIG. 7, the flap 84′ (and 86′, not shown) in the closedposition would lie adjacent the connecting members, and extendunderneath the connecting member (e.g. connecting member 21 a′) to lieagainst the vessel wall as shown in FIG. 7A, thereby inhibiting bloodflow.

It should be appreciated that the membrane extends at an angle acrossthe vessel of about 50 to about 70 degrees to help direct the blood flowand continuously wash the membrane body to prevent blood stagnation.(Other angles are also contemplated) More specifically, blood contactingthe body portion of the membrane 50 in the open position will bedirected upwardly, along the concave surface, thereby washing themembrane body to wash away clots to reduce the likelihood of clotting.In the closed position, blood contacting the membrane body will bedirected downwardly along the angled body to wash the opposing side ofthe membrane to likewise reduce the likelihood of clotting.

As can be appreciated, the membrane 50 remains at substantially the sameangle across the blood vessel in the open (flow allowing) and closed(flow inhibiting) positions/conditions. That is, as shown in FIGS. 5Aand 5B, the upper region of the membrane 50 is adjacent one side of thevessel wall in the open (flow allowing) position. The upper regionremains adjacent the same wall in the closed (flow inhibiting) position.Similarly, the lower region of the membrane 50 is adjacent an oppositeside of the vessel wall, and remains adjacent that wall in both the openand closed positions of FIGS. 5A, 5B, respectively. Thus, the upper andlower attached regions of the membrane remain in substantially the sameposition.

One example of the location of placement of the flow regulating devicein a patient's leg is shown in FIG. 8 with areas A1 and A2 showingpossible placement sites of the device, e.g. upstream or downstream ofthe native valve V.

If composed of shape memory, the device will automatically expand to theposition shown either upon release from a delivery member or in responseto temperature change. However, if composed of other materials, thedevice can be designed to automatically expand due to the springiness ofthe material or can alternatively be implanted in a blood vessel using aballoon catheter (not shown) as described in copending U.S. patentapplication Ser. No. 11/801,691, the entire contents of which areincorporated herein by reference. That is, rings 14 and 24 can be movedfrom a closed position to an expanded position by inflating the balloonor by use of a mechanical expander. Upon expansion, the rings 14 and 24apply a force against the vessel wall, thereby being retained therein.The balloon or mechanical expander is then deflated and the catheter isremoved from the blood vessel so the device 10 can regulate the flow ofblood through the vessel in the manner described above.

In the embodiments disclosed herein showing substantially circularrings, it should be understood that the rings can be shaped to have asize larger than the diameter of the vessel and therefore, depending onthe size of the vessel, may not assume a circular shape but have an ovalshape pressing against the vessel wall toward a circular configuration.

Referring now to FIGS. 9-11, there is shown a frame for a flowregulating device constructed in accordance with another preferredembodiment of the subject invention, and designated generally byreference numeral 200. Regulating device 200 includes an elongated frame220 that consists of upper and lower substantially annular ring portions240 and 260, much as described above. Rings 240 and 260 are connected toone another by at least one connective member 280 in the form of anx-shaped bar or wire. In the exemplary embodiment of FIGS. 9-14, twox-shaped connective members 280 are shown. Connective members 280 areadapted and configured to follow the circumference of the host vessel.The individual cross-linked bars or wires of each x-shaped connectivemember 280 are attached to the opposed rings 240 and 260 of frame 220 atlocations that are about 180° apart from one another, making device 200substantially symmetrical. This gives frame 220 an inherent symmetricalflexibility and enables it to move with the natural movements (e.g.,pulsitile) of the vein.

FIGS. 12-14 show device 200 with the membrane, much as described above,in place. Membrane or sail 250 attaches to portions of the x-shapedconnective members 280. Apertures 270 allow blood flow in one direction,and inhibit flow in the opposite direction much as described above. Thisframe and sail configuration gives device 200 more support and symmetry,allows for delivery using a simpler delivery device, distributes stressmore evenly and reduces stress raisers between support portions.

Although the blood flow-regulating device of the subject invention hasbeen described with respect to preferred embodiments, those skilled inthe art will readily appreciate that changes and modifications may bemade thereto without departing from the spirit and scope of the subjectinvention. While the above description contains many specifics, thosespecifics should not be construed as limitations on the scope of thedisclosure, but merely as exemplifications of preferred embodimentsthereof. Those skilled in the art will envision many other possiblevariations that are within the scope and spirit of the disclosure.

1. An implantable device for regulating blood flow through a bloodvessel, comprising: a) an elongated support dimensioned and configuredto be implanted in a blood vessel, the support including axially spacedapart first and second substantially annular support portions, and anx-shaped linking member linking the axially spaced apart portions to oneanother; and b) a valve membrane extending between the axially spacedapart support portions and having an upper portion, a lower portion andan intermediate portion, the valve membrane including a first region anda second lower region, the first region folded over the linking memberfor attachment and the second region being adjacent the first region andunattached to the linking member, the second region movable between afirst position to enable blood flow and a second position to inhibitblood flow.
 2. The device of claim 1, further comprising a third regionfolded over for attachment to the linking member, the second regionpositioned between the first and third regions.
 3. The implantabledevice as recited in claim 1, wherein the linking member includes twocurved members intersecting one another to form an x-shape.
 4. Animplantable device as recited in claim 1, wherein the support is formedat least in part from a shape memory alloy material.
 5. The implantabledevice as recited in claim 1, wherein the valve membrane is formed atleast in part from ePTFE.
 6. The implantable device as recited in claim1, wherein the valve membrane is coated at least in part with ananti-clotting agent.
 7. The implantable device as recited in claim 1,further comprising a second x-shaped linking member, wherein the valvemembrane includes a fourth region folded over the second linking memberfor attachment.
 8. An implantable device as recited in claim 1, whereinthe upper portion of the valve membrane is attached to a bottom regionof the first support portion and the lower portion of the membrane isattached to a top region of the second support portion.
 9. Theimplantable device of claim 8, wherein a section of the lower portion ofthe membrane is wrapped around a section of the top region of the secondsupport portion.
 10. An implantable device as recited in claim 1,wherein the support is integrally formed from a laser cut tube.
 11. Animplantable device for regulating blood flow through a blood vessel,comprising: a) an elongated support dimensioned and configured to beimplanted in a blood vessel, the support including axially spaced apartfirst and second substantially annular support portions, a firstx-shaped linking member linking the axially spaced apart portions to oneanother, and a second x-shaped linking member opposed to the firstlinking member and linking the axially spaced apart portions to oneanother; and b) a valve membrane supported by the support and includingfirst, second and third portions, the first portion attached at a firstregion of the support, the third portion attached at a second region ofthe support, and the second portion positioned between the first andthird portions and unattached to the support, the second portion movablewith respect to the support between a first position to enable bloodflow and a second position closer to the support to inhibit blood flow.12. The implantable device of claim 11, wherein the first and a thirdportions of the valve membrane form a flap wrapped around a portion ofthe support, and the second portion forms a flap movable with respect tothe first and third portions to create an opening for antegrade bloodflow.
 13. The implantable device of claim 12, wherein the second portionof the valve membrane is closer to a top region than a bottom region ofthe valve membrane.
 14. The implantable device of claim 11, wherein thevalve membrane further comprises a fourth portion separate from thesecond portion and unattached to the support, the fourth portion movablewith respect to the support between a first position to enable bloodflow and a second position to inhibit blood flow.
 15. The implantabledevice of claim 14, wherein the second portion forms a first flapadjacent the first linking member and the fourth portion forms a secondflap adjacent the second linking member, the flaps each creating a spacebetween the respective flap and the respective linking member duringantegrade blood flow to enable blood flow through the space and therespective flap closing the space during retrograde blood flow.
 16. Animplantable device for regulating blood flow through a blood vessel,comprising: a) an elongated support dimensioned and configured to beimplanted in a blood vessel and engageable with a blood vessel wall, thesupport including axially spaced apart first and second support portionsand an x-shaped linking member linking the axially spaced apart portionsto one another; and b) a valve membrane attached to the linking member,the valve membrane having an upper portion attached to a first sectionof the support and a lower portion attached to a second section of thesupport, the valve membrane having an enabling condition to enable bloodflow when blood flows in one direction and an inhibiting condition toinhibit blood flow when blood flows in an opposite direction, the upperattached portion of the membrane and the lower attached portion of themembrane remaining substantially fixed in position in both the enablingcondition and the inhibiting condition and the lower and upper attachedportions remaining adjacent opposing regions of the vessel wall in bothconditions.
 17. The implantable device of claim 16, wherein the valvemembrane includes an intermediate portion between the upper and lowerattached portions, and further includes a first flap in the intermediateportion, the first flap unattached to the support and movable forcreating the flow inhibiting and flow enabling conditions while theupper and lower attached portions remain substantially fixed inposition.
 18. The implantable device of claim 16, wherein the valvemembrane has a first region unattached to the support, the firstunattached region formed by at least one cut in the membrane, the firstunattached region creating a first opening adjacent the support duringantegrade blood flow.
 19. The implantable device of claim 18, whereinthe valve membrane has a second region unattached to the support, thesecond unattached region formed by at least one cut in the membrane, thesecond unattached region creating a second opening adjacent the supportduring antegrade blood flow.
 20. The implantable device of claim 19,wherein the first and second openings create a cross sectional shaperanging from about 15% to about 30% of the diameter of the vessel.